Steel alloys for making magnetic recordings



STEEL ALLOYS FOR MAKING MAGNETIC RECORDINGS Karl Appel, Hagen-Fley, Germany, assignor to Firma Stahlwerk Kabel, C. Pouplier, Jr., Hagen-Kaine], Germany No Drawing. Application December 24, 1954 Serial No. 477,592

4 Claims. (Cl. 75-128) 16l9% Cr, 6l2% Ni, and up to 0.3% C, 16-20% Cr, 615% Ni, and 0.22.5% Mn, 12-25% Cr, 55-14% Ni, and 0.060.2% C.

In every case mentioned, the steels contain metastable austenite, which is completely or partly converted into magnetic ferrite by cold forming operations.

For correct and uniform rendering of sounds it is necessary that the magnetic recording materials have a high coercive force and at the same time suflicient retentivity. Tendencies in the art are for improvements by proper selection of materials and manufacturing methods; in this respect, endeavors are made to improve the quality of a recordirng tape or wire to such a degree that not only sounds of low frequency, but also those of high frequency, often occurring in musical recordings, will be rendered clearly and evenly. This involves an increase in the coercive force to above 300 oersted, whereas conventional chromium-nickel recording wire rarely exceeds a coercive force of 200 oersted even with comparatively good alloy composition and special manufacturing methods.

It is the object of the present invention to provide improvements in the material for magnetic recordings. This is accomplished, according to the invention, by using nickel-manganese alloys with or without addition of chromium, in which the content of manganese is so adjusted with respect to the nickel content and the contents of the other components that no formation of stable austenite will occur.

Generally speaking, the alloy is composed of manganese-nickel steels, of metastable austenitic structure, containing 0.8- manganese, 15-40% nickel, about 0.1-2% silicon, from 03-15% carbon, balance iron and usual minor impurities. The material may be used as tape or wire for making magnetic recordings.

In addition to the components above mentioned, chromium may be contained in amounts up to 8%. When Cr is added, Ni can be reduced, as a rule. Addition of Cr increases the rust-proofness.

Further additions are, if desired, molybdenum up to 3%, tungsten up to 5%, nitrogen up to 0.2%, cerium up to 1%, thorium up to 1%, columbium up to 3%, titanium up to 3%, and tantalum up to 3%.

Up to 20% cobalt can be added instead of chromium or in addition thereto.

Of these various additions, molybdenum also acts as ice 2 rust-proofing agent, tungsten and cobalt improve the magnetic properties. Columbium, thorium, cerium, and tantalum do not influence the properties of the steel directly, but they act as deoxidants during production and therefore permit to obtain steels of higher purity.

Nitrogen and nickel are, to a certain extent, interdependent; consequently, nitrogen is capable of replacing nickel to a certain extent.

Thus, while the steels as generally stated, i. e. comprising the specified amounts of manganese, nickel, silicon and carbon, are very satisfactory per se, they are yet better by the various additions set forth.

The invention will now be described in a number of examples, but it should be understood that these are given by way of illustration only, and not by way of limitation.

Example] A wire having a diameter of 0.09 mms. is made of an alloy having the following composition:

Percent C 0.63 Si 0.23 Mn 1.46 Ni 19.52 Balance iron.

The coercive force was found to be 330 oersted, and rendering of sounds up to very high frequencies is excellent.

Example 2 A Wire having a diameter of 0.05 mms. is made of an alloy having the following composition:

Percent C 0.52 Mn 1.10 Si 0.39 Ni 20.10 Balance iron.

This alloy has a coercive force of 582 oersted, retentivity of 2480 gauss, at field intensity of 900 oersted.

Example 3 An alloy of the same composition was made into a wire having a diameter of 0.09 mms.

The coercive force in this case is 551 oersted, retentivity 2060 gauss.

was shaped into a wire of 0.05 mms. diameter.

The coercive force is 690 oersted, retentivity 1805 gauss, at field intensity 900 oersted.

Example 5 An alloy as described in Example 4 is shaped into a Wire having a diameter of 0.09 mms.

The coercive force is 656 oersted, retentivity 1690 gauss, at field intensity 900 oersted.

The values of coercive force of the materials made according to Examples 1-5 are about twice those of wires made from ordinary chromium-nickel steels as normally used for magnetic recordings.

Example 6 An alloy have the following components:

Percent C 0.5 3 Cr 2.49 Ni 19.25 Mn 1.54 Si 0.21 Balance iron.

This alloy is made into a wire having a diameter of 0.05 mms.

Coercive force 450 oersted, retentivity 3000 gauss, at field intensity 900 oersted.

In comparison to the wires or tapes made from the currently used chromium-nickel steels outlined in the beginning, the wires or tapes made from the materials according to the invention are by far superior as shown by their characteristics.

What I claim is:

l. A steel alloy for materials used in making magnetic recordings with high frequency sounds, said alloy having metastable austenitic structure and a coercive 4- force of at least 300 oersted; and containing from 0.8 to 5% manganese, 15-40% nickel, about 2.5 chromium, about 0.21-2% silicon, 03-15% carbon, balance iron, and minor amounts of impurities.

2. A steel alloy for materials used for making magnetic recordings, according to claim 1, containing in addition up to 3% of molybdenum.

3. A steel alloy for materials used for making magnetic recordings, according to claim 1, containing in addition up to 5% of tungsten.

4. A steel alloy from materials used for making mag netic recordings according to claim 1, containing in addition from 3 to 5% of a carbide-forming element.

References Cited in the file of this patent UNITED STATES PATENTS Elman June 4, 1929 Du Bois Sept. 18, 1951 OTHER REFERENCES 

1. A STEEL ALLOY FOR MATERIALS USED IN MAKING MAGNETIC RECORDINGS WITH HIGH FREQUENCY SOUNDS, SAID ALLOY HAVING MATASTABLE AUSTENITIC STRUCTURE AND A COERCIVE FORCE OF AT LEAST 300 OERSTED; AND CONTAINING FROM 0.8 TO 5% MANGANESE, 15-40% NICKEL, ABOUT 2.5 CHROMIUM, ABOUT 0.21-2% SILICON, 0.3-1.5% CARBON, BALANCE IRON, AND MINOR AMOUNTS OF IMPURITIES. 